Gender differences in the order of appearance of elbow ossification centres

Background The predictable order of appearance of elbow secondary ossification centres in children is important in interpreting elbow radiographs, most commonly in the context of trauma. The usual sequence of appearance of these ossification centres is given by the acronym CRITOL, but exceptions have been described and are recognised as normal variants. Aim To investigate the extent to which the appearance of the elbow secondary ossification centres follows a predictable sequence, and to establish the incidence of exceptions to the usual CRITOL order. Methods Two-stage retrospective review of 421 elbow radiographs in children at our centre. Results Of 64 children with two visible ossification centres, there was a 23% overall variant incidence (49 CR, 15 CI). Twenty-eight children had four visible ossification centres, with an overall variant incidence of 32% (19 CRIT, 9 CRIO). The variants were significantly more common in girls than in boys (p < 0.001). Conclusion Whilst the majority of radiographs remained consistent with the described CRITOL sequence, variance in this order was seen in a quarter of children with two visible ossification centres, and a third of children with four visible ossification centres. Incidence of variance was much more common in girls, reaching statistical significance. Awareness of these normal variations, particularly in girls, should help to avoid misinterpretation.